Color display devices, such as computer monitors and television sets, typically include thousands of individual pixels. A pixel is a discrete picture element that, for example, can generate a range of colors at a particular location on a display screen. Pixels are typically arranged in an array of columns and rows. Collectively, the pixels can be used to form an image. For example, each pixel corresponds to a dot, and a combination of thousands of dots having various different colors and intensities produces a viewable image on a display screen.
Conventional display devices use an additive color mixing process. Using additive color mixing, each pixel on a display screen or projector is produced using an RGB (red-green-blue) representation. Different proportional combinations of red, green, and blue components can be used to produce a wide range of colors. In an RGB display, each pixel includes three adjacent sub-pixels—one red sub-pixel, one green sub-pixel, and one blue sub-pixel. A single pixel can be generated from the combined light of the three sub-pixels, and, by controlling the intensity of each sub-pixel, the pixel can be adjusted to produce a wide range of visible colors. Thus, each pixel is an additive mixture of varying proportions of the three primary colors, which are added to an effectively black background.
Printers on the other hand generally produce colors through a subtractive color mixing principle. In particular, varying amounts of different tinted inks are applied to a sheet of white paper in layers. A typical color printer, for example, includes cyan, magenta, yellow, and black (CMYK) inks. Each layer subtracts some of the light from the white background, and the combination of the layers results in light of a particular color. By using different proportional amounts of the tinted inks in the layers, a wide range of visible colors can be produced. Thus, colors are produced on a page by subtracting selected proportions of different wavelengths of light from an effectively white background.
Because of the different mixing principles used in additive RGB display devices and subtractive CMYK printers, it is necessary to perform conversions between parameters of color mixing models associated with such display devices and printers. For example, an RGB model for a particular display device uses a corresponding set of parameters to define an intensity of each RGB sub-pixel to produce a specific color. A CMYK model for a particular printer uses a similar set of parameters to define an amount of each CMYK ink to produce a specific color. To print an image that is represented on a display screen, a conversion between the parameters of the two models is necessary.